Clean Colonoscopy Grants 5-Year Relief

Sept. 17, 2008 -- People who get an "all clear" after colonoscopy screening don't get colon cancer for at least five years, a new study confirms.

Current U.S. guidelines say that if your colonoscopy finds no polyps or suspicious lesions, you won't need another colonoscopy for 10 years.

Many U.S. gastroenterologists say they call patients back much more often than that. Why? The evidence has been thin.

Now there's more evidence from Thomas F. Imperiale, MD, of Indiana University; David F. Ransohoff, MD, of the University of North Carolina at Chapel Hill; and colleagues.

The researchers found no colon cancers in 1,256 healthy men and women rescreened five years after their first negative colonoscopy.

"Once someone has had a negative initial colonoscopy, there is no need for that person to have another colonoscopy sooner than five years after that screening," Ransohoff says in a news release.

Sixteen percent of those rescreened had grown new polyps, which are suspicious growths that can slowly become cancers. Only 1.3% of study participants had "advanced adenomas," which are much more suspicious but which are not necessarily destined to become cancers.

"There is uncertainty about the clinical importance of 'advanced adenoma' and its appropriateness as a target in programs of screening and surveillance," Imperiale and colleagues write in their report.

"We did not assess the appropriateness of the recommended 10-year rescreening interval for colonoscopy," Imperiale and colleagues note.

Even so, the new data should make doctors more comfortable with current recommendations, notes an editorial by Robert H. Fletcher, MD, professor emeritus at Harvard University.

"It is in the best interests of both patients and society to extend screening intervals as far as it is safe to do," Fletcher suggests. "Now we can be more confident that judgments made by expert groups, on the basis of lesser evidence, were correct."

The Imperiale report, and the Fletcher editorial, appear in the Sept. 16 issue of The New England Journal of Medicine.